Observation of half-integer Shapiro steps in graphene Josephson junctions

We study quantum transport and AC Josephson effect of hexagonal boron nitride encapsulated graphene (BGB) Josephson junctions (JJs). Our experiments reveal the emergence of the half-integer Shapiro steps in the n-type regime with high electron carrier densities. We attribute this observation to the gate-tunable transmission probability of the graphene junction. Our numerical simulations are consistent with the appearance of half-integer Shapiro steps at high transparency, which suggests a skewed current phase relationship in the graphene JJ.

Automated summary

We study quantum transport and AC Josephson effect in hexagonal boron nitride encapsulated graphene Josephson junctions. The emergence of half-integer Shapiro steps in the n-type regime with high electron carrier densities is observed. This observation is attributed to the gate-tunable transmission probability of the graphene junction. Numerical simulations support the appearance of half-integer Shapiro steps at high transparency, indicating a skewed current phase relationship in the graphene Josephson junction.